The present invention relates to a method of fabricating an adhesive sheet formed of a surface sheet, an adhesive layer coated on the back side of the surface sheet and a release sheet for protecting the adhesive layer. More particularly, the invention relates to a method of fabricating an adhesive sheet having one or more slender non-adhesive coated areas, along the longitudinal direction of the sheet, in an adhesive layer interposed between a surface sheet and a release sheet.
An adhesive sheet has an adhesive or a pressure-sensitive adhesive coating layer on a surface sheet such as paper, cloth or film, and the adhesive sheet further has a release sheet made of paper, cloth or film as a base material ordinarily bonded to the adhesive coating layer so as to prevent the adhesive sheet from sealing or adhering to each other. The release sheet prevents the adhesive coating layer from being exposed. Such an adhesive sheet is generally fabricated by a method comprising of coating an adhesive on one side surface of a release sheet having a wide width continuously fed from a roll, then drying the adhesive coating layer to form an adhesive layer on the release sheet, and then bonding a surface sheet of wide width continuously fed from a roll to the adhesive layer. The adhesive sheet can be also fabricated by a method comprising of coating an adhesive on a surface sheet to form the adhesive layer instead of coating an adhesive on the release sheet, and then bonding the release sheet to the adhesive layer.
Irrespective of coating the adhesive on the release sheet or the surface sheet, it is customary to wind the adhesive sheet of wide width thus fabricated on a roll, and to cut the adhesive sheet in a suitable width or to feed the adhesive sheet out and to wind the sheet on other rolls while longitudinally cutting the sheet in a suitable width and then to supply the cut sheet to the step of forming the sheet in labels, stickers or tags. Thus, it is preferable at a point of view of non-contaminating cutting blades and rolls of a cutting machine with the adhesive that the adhesive layer of the adhesive sheet to be cut is of non-adhesive coated areas. In this case, since portions that do not adhere of the adhesive sheet after cutting remain widely if the width of the non-adhesive coated areas is excessively wide, it is necessary to accurately form the non-adhesive coated areas in an intended narrow width. Further, the adhesive sheet formed in labels, stickers or tags is bonded to the surface of an article for end use purpose after separating the release sheet from the adhesive layer. Therefore, it is convenient to form a non-adhesive coated area on the adhesive sheet so as to separate the release sheet from the adhesive sheet by readily grasping the release sheet by fingers or other means. Moreover, it is also preferable at a point of view of non-contaminating cutters and rolls in an apparatus that makes marginal holes that the marginal hole portions are of non-adhesive coated areas even when the marginal holes are formed at one or both sides of the adhesive sheet. However, if an adhesive is coated and dried on the entire surface of the surface sheet or the release sheet in case of fabricating the adhesive sheet, the adhesive sheet having the non-adhesive coated area cannot be provided.
The following methods exist as a method of fabricating a sheet having a non-coated area. One is, as disclosed in GB1349173 (Japanese Patent Application Laid-open No. 25503/1973), a method of fabricating a sheet by coating a coating liquid on a sheet by an applicator roll, and scraping the coating liquid on the roll circumferentially by a doctor blade before the roll makes contact with the sheet. The other is, as disclosed in Japanese Patent Application Laid-open No. 69238/1978, a method of fabricating a sheet by using a coating device in which a partition plate extending upwardly from a bath level of a coating liquid bath is installed vertically with respect to the rotational shaft of an applicator roll in contact with the surface of the roll in the bath in which the lower part of the roll is dipped. According to this method, the partition plate can prevent the coating liquid from being applied to the roll, and a non-coated area slender in a circumferential direction can be formed in the coating layer on the surface of the applicator roll.
However, the application of the above-described methods to fabricate the adhesive sheet does not meet with good results since the adhesive has relatively high viscosity such as 2000 to 9000 cps and frequently 2000 to 6000 cps at 20.degree. C. Since pressing pressure is applied to the adhesive layer in case of pressing a surface sheet or a release sheet to the adhesive layer having a non-adhesive coated area formed on the surface of the applicator roll to transfer the adhesive layer to the sheet, the adhesive layer is extended laterally to the non-coated area. Thus, the width of the non-adhesive coated area transferred to the sheet is narrowed irregularly as compared with the width on the applicator roll. In other words, it is substantially impossible to transfer the adhesive layer having the same width of the non-adhesive coated area as that of the non-adhesive coated area on the applicator roll to the sheet by pressing the adhesive layer prepared on the roll with the non-adhesive coated area of the intended width on the surface sheet or the release sheet. Since it is not rare to form the width of the non-adhesive coated area in milli-meter order in case of forming the non-adhesive coated area on the adhesive sheet, the above-described fact is very inconvenient to fabricate the adhesive sheet.